Sootopolis City Gym

The Sootopolis Gym is the final gym in the Hoenn region. However, the Gym is unaccessable until you stop Kyogre (Sapphire Version) or Groudon (Ruby Version) or summon Rayquaza (Emerald Version). In Ruby and Sapphire, the Gym Leader is Wallace. In Emerald, the Gym Leader is his mentor, Juan. Both use Water-type Pokémon. The Puzzle is to step over the ice tiles once. If you step on an ice tile twice you will fall to the floor below and face the gym trainers (which are all female).